Modern nanotechnologies allow finding new opportunities even in “eternal values”, such as for instance gold. Surprisingly, but in the nanoworld the so well-known gold transforms to acquire new properties. Thus, it may lose its metal qualities and get semi-conductor features; and when oxidized, nanogold demonstrates magnetic properties.
There has already been developed a number of ways to produce nanogold particles, as for instance the method of Turkevich or that of Brust. There are methods to stabilize synthesized nanoparticles in solutions (electrostatic, adsorption and shemisorption methods). In particular, Nanomet, a Moscow-based research company (http://www.nanomet.ru), is producing standardized nanoparticles (15 nm), which may be used both as micellar and aqueous solutions and for obtaining liquid-phase and solid materials modified by nanoparticles which in the process acquire high-level bioactive, catalytic and other practical and useful properties.
1. Medicine
Nanogold-based biomarkers are admitted to be the main feature of this material. Nanosphere, Inc., a U.S.-based company, has developed and patented (85 patents!) a series of methods for high-speed diagnostics of mass diseases. This has found its application in simple and cheap a) genetic testing and b) protein diagnostics. The last one was used to detect cardiovascular deviations and prostate cancer (by way of PSA, a prostate-specific antigen) at their early stages. The company has developed diagnostic equipment called the Verigene® System. It is engaged in developing diagnostic methods for two other types of cancer using P53 protein used to control mammary gland cancer and thyroglobulin to check recurrent thyroid cancer, as well as a test method for Alzheimer’s disease.
A group of Israeli scientists has studied a method for early diagnosis of lung cancer. Nanosensors detect the so-called unstable organic particles in the patient’s breath and such particles appear to be the first signs of illness. The device is cheap enough and can fill up the family doctor’s toolkit. It allows predicting lung cancer in 86% of cases.
Nuclear physicists from Dubna, a Russian scientific center near Moscow, have suggested using nanogold to treat oncological diseases. The main advantage of the invented method is that irradiation does not affect healthy cells. After introducing their preparation into the human body nanogold particles settle on cancer cells. Then they are heated with microwave radiation. Since gold is a good heat conductor, cells are heated up one thousand times more quickly than healthy tissues. This method facilitates destruction of malignant formations.
2. Computer memory
The Taiwan researchers from the Chun Hsing National University (NCHU) and the Industrial Technology Research Institute (ITRI) have developed a simple and inexpensive memory representing an array based on a combination of plastic and gold nanoparticles. It is planned to apply such memory to create flexible electronics, such as radio-frequency identifiers, smart cards, electronic paper, mobile phones, etc. New memory can be made of readily available materials and it can be very cheap in manufacture. Nevertheless, at the current stage of technological development, its huge drawback consists in a very small quantity of recording cycles - latest measurements showed that its memory does not maintain more than 1000 cycles of state changes and keeps data for approximately 10 days. The new memory is made of gold nanoparticles and polymeric compounds. To read and record, as well as to delete data from a memory cell it is necessary to apply different voltages.
The employees of the Swinburne University of Technology in Australia managed to develop an optical disk of high capacity - up to 1.6 TB. It was achieved by introducing gold nanoparticles into the disk structure and using lasers of various wave length – 700, 840 and 980 nanometers. Besides, improving this technology it is possible to increase the capacity of a single disk up to 10 ТБ. Samsung, Korea, has been reported to contract the developers for commercial manufacture of appropriate carriers and drives.
3. Catalysts
Nanogold appeared to be an active enough catalyst for some chemical reactions. British scientists, for instance, working in team with Johnson Matthey, a well-known company in the field, investigated selective hydrocarbon oxidation. Similar research is being performed by the Tokyo Metropolitan University to convert unsaturated hydrocarbons to oxygen-containing organic compounds (e.g., epoxides, ketones).
Nanogold is also effective to convert harmful carbon monoxide to harmless carbon dioxide at low temperatures. Such facilities are produced for example by Novax Material & Technology, Taiwan.
Gold particles the size of 2 to 15 nanometers, especially if treated with bismuth additives, can act as a catalyst in a number of other reactions.
4. Nanoprinting
The IBM Laboratories in Zurich have developed a technique permitting to set locations for single nanoparticles with high accuracy, and also, which is very important, to produce equipment for practical application of the offered methods. In this new technique, the researchers spray a thin layer of nanoparticles on plates, allowing them to fill grooves. After drying the “ink,” a thin polymeric layer is used to fix nanoparticles on the target surface. As a result of this operation, you may get pictures, which are thousand times more detailed compared to those obtained by classic methods. This invention may turn useful for manufacturers of biosensors, ultrathin lenses, nanowire and other subminiature components of electronic systems.
Johnson Matthey has produced nanoink which may be used to make gold inscriptions on glass and semiconductors at a room temperature; gold in this ink is stabilized by organic additives belonging to the amine group. Inscriptions are made by a special piezo-printer. Nanoink has a potential application perspective for manufacturing corrosion-proof contacts in microelectronics with an estimated market capacity of 3 tons a year.
It is remarkable, that hi-tech gold nanoinscriptions have also caught on with the jewellery business. Thus, Mir Enterprises recently displayed sapphires graced with nanogold lines from Koran which had been inscribed by an electron beam.
Vladimir Teslenko for Rough&Polished
